One of the essential problems for establishing a sustainable society for human beings without destroying the material circulation system on the limited earth, is to create renewable clean energy which does not use an exhaustible resource such as fossil fuel or uranium or destroy the resource environment. That is, renewable energy has been demanded which discharges a small amount of harmful substances when being converted to effective energy such as electricity and heat so as to be used by human beings and which is produced by using permanently usable energy sources such as sunlight, wind power, water power, natural steam, and biomass. Practical use of these energy sources is increasing because of their attractive characteristics. However, in any case, there are various inherent problems concerning the final costs.
In the case where biomass is used as an energy source, energy conversion is performed using heat which is obtained by directly burning organic waste derived from living resources, or carbonized, liquefied, or gasified fuel. Accordingly, this case has the feature of making a significant contribution over establishment of a recycling-based society, which results in reuse of waste or reduction in waste, but has not only an infrastructure-relating problem in that the cost for collecting, delivering, and managing the resources is required because such resources are dispersed over a wide range, but also a technical problem in that the combustion efficiency or the efficiency of conversion to fuel is not good, for example. Accordingly, various systems including an organic waste carbonizing system (NPL 1) and a charcoal syngas production system (PTL 1) have been developed.
In particular, a system disclosed in PTL 2, including: decomposing organic waste into gas (CO, H2, CH4, CO2, H2O), carbide, and hydrocarbon under a low-oxygen condition at high temperature (200 to 600° C.); generating water gas (mixed gas containing, as main contents, hydrogen gas, carbon monoxide gas, and carbon dioxide gas) through a pyrolysis reaction between the carbide and superheated water steam (hereinafter, also referred to as “steam”) which is a gasification agent; and using the water gas as fuel for power generation, is interesting as a biomass fuel production process and power generation system including a series of an organic waste carbonization process, a gasification process, and a power generation process. Furthermore, NPL 2 reports an attempt to produce hydrogen from water gas generated by direct gasification of biomass.
Therefore, for carbonizing furnaces, pyrolytic furnaces, and water gas generation systems, hydrogen gas generation system, and power generation systems including these furnaces, the following technologies have been conventionally developed.
For example, carbonizing furnaces are known which carbonize organic waste with combustion heat generated by partial combustion of the organic waste. When organic waste is partially burned in such a carbonizing furnace, solid material containing much carbide and combustion gas containing combustible gas are generated. In particular, a carbonizing furnace disclosed in PTL 3 includes a carbonizing unit which is formed in the upper portion of a region formed between a substantially cylindrical main body and a cylindrical body accommodated in the main body and which carbonizes solid material containing much carbide, and a non-combustion unit which is formed in the lower portion of the region and which extinguishes fire burning carbide. This carbonizing furnace enables combustion of combustible gas, which is contained in combustion gas generated by partial combustion of organic waste, in a secondary combustion unit disposed in the upper portion of the carbonizing furnace.
Also, for example, pyrolytic furnaces are known which cause pyrolytic reactions of carbide, which is generated by partial combustion of organic waste, by heating the carbide together with a gasification agent such as water vapor, and thereby generate water gas. In particular, a pyrolytic gasification furnace disclosed in PTL 4 includes an outer cylinder and an inner cylinder, and is configured to supply carbide and a gasification agent to the inner circumference side of the inner cylinder and to supply combustion gas generated by a carbonizing furnace to a gap between the outer cylinder and the inner cylinder. High-temperature combustion gas is supplied to the gap. Accordingly, the outer circumferential surface of the inner cylinder is heated by the combustion gas, so that a pyrolysis reaction on the inner circumference side of the inner cylinder can be promoted.
In addition, a water gas generation system for generating, in the pyrolytic furnace, water gas from carbide supplied from the carbonizing furnace, and further, a power generation system using the water gas are disclosed in PTL 2 and PTL 4, for example.
Meanwhile, as disclosed in NPL 2, for example, a hydrogen gas producing technology enables production of hydrogen from raw material gas which is obtained by directly gasifying wood chips or waste plastics with a high-temperature water steam and which contains hydrogen gas and carbon monoxide gas as main components. Such a technology is basically achieved by including a gasification facility and a hydrogen producing facility. The gasification facility is formed of a gasification furnace, a reforming furnace, an air preheater, a reformed-gas cooler, a dust filter, a gas cooling/purifying tower, a gas purifying facility, a pyrolytic reaction evaporator, a high-temperature steam generator, and the like. The hydrogen producing facility is formed of a pre-treatment apparatus, a carbon monoxide shift converter, and the like.